The truth is in the article, but surprisingly well hidden. Most of it is misunderstanding mid Victorian housing, or at the very least the term, and talks about derivatives not 2+2s. The key point of a 2+2 is the rooms are the full width of the house.
The floorplan shown is not a typical UK Victorian two up, two down. It's a three up, three down, sometimes called by estate agents an extended two up, two down. Count the rooms, it's not difficult. It's clearly heavily influenced by the 2+2. :)
The only point he gets it right is in the caption under the photo further on down the article:
Note that the houses in the foreground are built along more generous lines than those at the back, with bow windows on both floors and an extra room built above the projecting ground-floor kitchen
Yes, three up, three down, or as the the aerial photo two up, two down, with attached kitchen/bathroom. More like the shown floorplan to allow an extra third room on each floor, one of which being the then new innovation of indoor bathroom/toilet.
A two up, two down has a feature that the rooms are the full width of the house: reception, with kitchen in back -- one of those two has the stairs within it, the second floor has two bedrooms and a "landing" that's often just the width of the stair treads and two doors at the top. The toilet is outside by the coal house, and the bath was tin, hung up in the kitchen when not used, often under the stairs. They have often gained a 20th century replan or rear extension to permit the indoor bathroom/toilet, and frequently larger or separate kitchen underneath -- though many have kitchen and bathroom in a single ground floor extension.
Nowt else is a two up, two down, they're relatives, derivatives. Many mid Victorian 2+2 terraces came with colossal garden plots - 150-300 foot long, giving loads of scope for later indoor bathrooms, kitchens, and garages -- sometimes double length at the far end.